CN101215348B - Polymerization method for low molecule polytetrafluoroethylene resin - Google Patents
Polymerization method for low molecule polytetrafluoroethylene resin Download PDFInfo
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Abstract
The invention relates to a process for polymerization of low-molecular polytetrafluoroethylene resin, which belongs to the technical field of chemical production. The process comprises utilizing deionized water to be reaction medium, adding a little amount of molecular weight conditioning agent, polymerizing under an initiation system of peroxodisulfate, obtaining fine particles namely polytetrafluoroethylene emulsion after handling polymer which is got, and obtaining concentrated solution or polytetrafluoroethylene particles after handling the emulsion which is obtained. The invention provides an emulsion polymerization system which utilizes aqueous medium ammonium peroxodisulfate to be initiating agent without using dissolvent and without handling terminal group, and the process has the advantages of even molecular weight distribution, even molecular weight distribution, and even grain-size distribution, which is beneficial for industrial production.
Description
The low technical field
The present invention relates to a kind of polymerization process of low molecule polytetrafluoroethylresin resin, belong to chemical production technical field.
Background technology
Teflon resin is because its molecular weight is big, and the fluorine atom radius is big, shield effectiveness good, makes it have superior mechanical property, electrical property, chemical property, weather resistance.The molecular weight of tetrafluoroethylene is usually 100～1000 about ten thousand.The low molecule polytetrafluoroethylresin molecular weight is generally below 10% of tetrafluoroethylene, owing to be made of carbon atom and fluorine atom fully in the polymkeric substance, hc-surfactant is in removal, has fluorine material aspect high-performance fully though molecular weight is little.Has good high temperature resistant and weathering resistance.Simultaneously low molecule polytetrafluoroethylresin is because particle is little, and sintering temperature is low, membranous advantage such as close.
At present, domestic molecular weight is less than the preparation of 100,000 tetrafluoroethylene, and is also less to the research of its performance and processing aspect.The low molecular industrialized preparing process of PTFE mainly contains two kinds at present, a kind ofly adopt the dairy industry polymerization process to realize by controlled polymerization speed by direct employing molecular weight regulator, second kind be with common high molecular weight polytetrafluoroethyldispersions through the radiation special processing, make fine powder again and make product.
The method research that adopt to add molecular weight regulator, foreign study are all continuous mutually its product of release of representative with U.S. DUPONT company with Japanese DAKIN company wherein relatively early, and domestic have a morning twilight chemical research institute.
Common method is to be raw material with the tetrafluoroethylene monomer, adopts emulsion polymerization, is medium with water or solvent and perfluoro solvent under certain temperature and pressure agitation condition, is emulsifying agent with the ammonium perfluorocaprylate.Persulphate is an initiator, carries out polymerization, adds difluorochloromethane (CHF in reaction process
2Cl) control the polymerization degree of tetrafluoroethylene for molecular weight regulator, obtain concentration, emulsion is condensed into low-molecular-weight tetrafluoroethylene under certain concentration and agitation condition at 20～35% dispersion emulsion.
As US005,789,504A prepares low molecular weight polytetrafluoroethylene, 250～325 ℃ of fusing points, polymeric reaction temperature-10～70 ℃, molecular weight regulator two fluoro-methyl chloride, the polymer fluid drying obtains the solid low molecular weight tetrafluoro ethylene resin after removing organic solvent, or after concentrating, obtain the organic medium suspensoid of high density low molecular weight polytetrafluoroethylene, with after its end group stabilization processing, obtain the lower molecular weight PTFE resin of stable performance then.Point out that simultaneously molecular weight regulator also can be a Perfluorocyclobutane.The polymer fluid that this technology obtains is comparatively stable, the initiator that adopts is an organo-peroxide, add-on 0.05～5wt% monomer wt, if it is very low to add too many PTFE molecular weight, the reaction times prolongs, and initiator is residual more in the solvent, therefore need handle the end group of PTFE, make its complicated and organic solvent need to reclaim, tail gas needs to handle, and makes its process complications.
Summary of the invention
Defective at prior art, the invention provides and a kind ofly do not use solvent, do not need end group is handled, made initiator emulsion polymerization system, even molecular weight distribution with the water medium ammonium persulphate, size distribution is even, helps the polymerization process of the low molecule polytetrafluoroethylresin resin of suitability for industrialized production.
A kind of polymerization process of low molecule polytetrafluoroethylresin resin, concrete grammar is as follows:
1) has the ammonium persulfate initiator of the ammonium perfluorocaprylate of the deionized water that adds 60 weight parts in the polymeric kettle of agitator, 0.4-0.5 weight part 10-15% and hc-surfactant TX-4 emulsifier mix solution, 0.02 weight part, airtight polymeric kettle, find time and use nitrogen wash, under the condition of oxygen level less than 30PPm, add 0.03 weight part molecular weight regulator ether again;
2) polymeric kettle is heated, when making the polymerization temperature in the kettle rise to 70 ℃, add tetrafluoroethylene monomer, make the pressure 0.8～3.0Mpa in the polymeric kettle, under the constant agitation condition, carry out the constant pressure polymerization reaction;
3) in reaction process since tetrafluoroethylene polymerization be strong exothermal reaction, along with the consumption of TFE, temperature constantly raises, stopped reaction when the polymerization temperature in the kettle reaches 90-95 ℃;
4) reclaim tetrafluoroethylene monomer, obtain solid content and be 18～30% lower molecular weight emulsion, the treated mechanical breakdown of emulsion cohesion of emulsion back obtains the low molecule polytetrafluoroethylresin resin of 3～6um after with deionized water wash, oven dry processing;
5) product is carried out analytical test, packing of product warehouse-in.
Step 2) in, the pressure in the preferred polymeric kettle is 0.8～3.0Mpa,
The method for preparing molecular weight is less than 100,000 PTFE resins, and having overcome the deficiency of solvent-borne type polymerization process and the polymkeric substance of acquisition needs to handle.
Superiority of the present invention is, polymerization starting stage temperature rises to higher level, finishes polymerization free radical in the later stage under comparatively high temps and fully stops, and the pressure of TFE carries out under constant pressure, polymerization temperature is higher than the critical temperature of TFE, avoids TFE liquid particle to occur like this and carries out polymerization.
The initiator that uses in the practice of the present invention is included in all effective TFE polymerization radical initiator of whole use temperature scope, initiator should produce the free radical of abundant quantity in reaction process, the initiator system that the initiator of embodiment is known in the art, initiator are superoxide.Initiator concentration influences polymerisate in the present invention, the consumption of initiator by the formation polymer weight 0.3～2%.
The stirring velocity of reactor among the present invention, be can increase TFE in water solubleness and molecular weight regulator is evenly dispersed in the water, can remove reaction heat fast in polymerization process.
The present invention provides a kind of method for producing molecular weight less than 100,000 tetrafluoroethylene, described resin is used for being added into coating and has low sintering temperature, the coating of dense structure, and the mould coating that can be widely used in rubber, plastics makes it be easy to peel off, and the film difficult drop-off forms crackle.Make it more meet different occasion various objectives, the coating of the mould that shape is special becomes possibility.
The emulsion solids thing content that obtains under polymerizing condition is by water dispersion evaporate to dryness of weighing and the gravimetric determination that takes by weighing the exsiccant solids.Solid contents is represented with the percentage ratio based on the mixed weight of PTFE and water.The emulsion granularity is measured by photon correlation spectroscopy.
The present invention has and does not use solvent, do not need end group is handled, made initiator emulsion polymerization system, even molecular weight distribution with the water medium ammonium persulphate, size distribution is even, helps suitability for industrialized production.
Embodiment
Embodiment 1:
The polymerization process of low molecule polytetrafluoroethylresin resin, concrete grammar is as follows:
1) ammonium persulfate initiator of the ammonium perfluorocaprylate of the deionized water of adding 60 weight parts, 0.4 weight part 10% and hc-surfactant TX-4 emulsifier mix solution, 0.02 weight part in having the polymeric kettle of agitator, airtight polymeric kettle, find time and use nitrogen wash, under the condition of oxygen level less than 30PPm, add 0.03 weight part molecular weight regulator ether again;
2) polymeric kettle is heated, when making the polymerization temperature in the kettle rise to 70 ℃, add tetrafluoroethylene monomer, make the interior pressure of polymeric kettle, under the constant agitation condition, carry out the constant pressure polymerization reaction to 2.0Mpa;
3) in reaction process since tetrafluoroethylene polymerization be strong exothermal reaction, along with the consumption of TFE, temperature constantly raises, stopped reaction when the polymerization temperature in the kettle reaches 90 ℃;
4) reclaim tetrafluoroethylene monomer, obtain solid content and be 23% lower molecular weight emulsion, the treated mechanical breakdown of emulsion cohesion of emulsion back obtains the low molecule polytetrafluoroethylresin resin of 3～6um after with deionized water wash, oven dry processing;
Embodiment 2:
The polymerization process of low molecule polytetrafluoroethylresin resin, concrete grammar is as follows:
1) ammonium persulfate initiator of the ammonium perfluorocaprylate of the deionized water of adding 60 weight parts, 0.4 weight part 15% and hc-surfactant TX-4 emulsifier mix solution, 0.02 weight part in having the polymeric kettle of agitator, airtight polymeric kettle, find time and use nitrogen wash, under the condition of oxygen level less than 30PPm, add 0.03 weight part molecular weight regulator ether again;
2) polymeric kettle is heated, when making the polymerization temperature in the kettle rise to 70 ℃, add tetrafluoroethylene monomer, make the pressure 2.0Mpa in the polymeric kettle, under the constant agitation condition, carry out the constant pressure polymerization reaction;
3) in reaction process since tetrafluoroethylene polymerization be strong exothermal reaction, along with the consumption of TFE, temperature constantly raises, stopped reaction when the polymerization temperature in the kettle reaches 90 ℃;
4) reclaim tetrafluoroethylene monomer, obtain solid content and be 24% lower molecular weight emulsion, the treated mechanical breakdown of emulsion cohesion of emulsion back obtains the low molecule polytetrafluoroethylresin resin of 3～6um after with deionized water wash, oven dry processing;
5) product is carried out analytical test, packing of product warehouse-in.
Embodiment 3:
The polymerization process of low molecule polytetrafluoroethylresin resin, concrete grammar is as follows:
1) ammonium persulfate initiator of the ammonium perfluorocaprylate of the deionized water of adding 60 weight parts, 0.5 weight part 10% and hc-surfactant TX-4 emulsifier mix solution, 0.02 weight part in having the polymeric kettle of agitator, airtight polymeric kettle, find time and use nitrogen wash, under the condition of oxygen level less than 30PPm, add 0.03 weight part molecular weight regulator ether again;
2) polymeric kettle is heated, when making the polymerization temperature in the kettle rise to 70 ℃, add tetrafluoroethylene monomer, make the pressure 2.0Mpa in the polymeric kettle, under the constant agitation condition, carry out the constant pressure polymerization reaction;
3) in reaction process since tetrafluoroethylene polymerization be strong exothermal reaction, along with the consumption of TFE, temperature constantly raises, stopped reaction when the polymerization temperature in the kettle reaches 90 ℃;
4) reclaim tetrafluoroethylene monomer, obtain solid content and be 24% lower molecular weight emulsion, the treated mechanical breakdown of emulsion cohesion of emulsion back obtains the low molecule polytetrafluoroethylresin resin of 3～6um after with deionized water wash, oven dry processing;
Embodiment 4:
The polymerization process of low molecule polytetrafluoroethylresin resin, concrete grammar is as follows:
1) ammonium persulfate initiator of the ammonium perfluorocaprylate of the deionized water of adding 60 weight parts, 0.5 weight part 10% and hc-surfactant TX-4 emulsifier mix solution, 0.02 weight part in having the polymeric kettle of agitator, airtight polymeric kettle, find time and use nitrogen wash, under the condition of oxygen level less than 30PPm, add 0.03 weight part molecular weight regulator second difluorochloromethane again, add 0.01-0.1 part R 1216;
2) polymeric kettle is heated, when making the polymerization temperature in the kettle rise to 70 ℃, add tetrafluoroethylene monomer, make the pressure 0.8～3.0Mpa in the polymeric kettle, under the constant agitation condition, carry out the constant pressure polymerization reaction;
3) in reaction process since tetrafluoroethylene polymerization be strong exothermal reaction, along with the consumption of TFE, temperature constantly raises, stopped reaction when the polymerization temperature in the kettle reaches 90-95 ℃;
4) reclaim tetrafluoroethylene monomer, obtain solid content and be 30% lower molecular weight emulsion, the treated mechanical breakdown of emulsion cohesion of emulsion back obtains the low molecule polytetrafluoroethylresin resin of 3～6um after with deionized water wash, oven dry processing.
Claims (1)
1. the polymerization process of a low molecule polytetrafluoroethylresin resin is characterized in that, concrete grammar is as follows:
1) ammonium persulfate initiator of the ammonium perfluorocaprylate of the deionized water of adding 60 weight parts, 0.4-0.5 weight part 10-15% and hc-surfactant TX-4 emulsifier mix solution, 0.02 weight part in having the polymeric kettle of agitator, airtight polymeric kettle, find time and use nitrogen wash, under the condition of oxygen level less than 30PPm, add 0.03 weight part molecular weight regulator ether again;
2) polymeric kettle is heated, when making the polymerization temperature in the kettle rise to 70 ℃, add tetrafluoroethylene monomer, make the pressure 0.8～3.0Mpa in the polymeric kettle, under the constant agitation condition, carry out the constant pressure polymerization reaction;
3) in reaction process since tetrafluoroethylene polymerization be strong exothermal reaction, along with the consumption of TFE, temperature constantly raises, stopped reaction when the polymerization temperature in the kettle reaches 90-95 ℃;
4) reclaim tetrafluoroethylene monomer, obtain solid content and be 18～30% lower molecular weight emulsion, emulsion through mechanical breakdown of emulsion cohesion back with deionized water wash, obtain the low molecule polytetrafluoroethylresin resin of 3～6um after drying processing.
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